新型含氧亚甲基和亚胺桥键的液晶化合物的合成及介晶性

Synthesis and Mesomorphism of New Liquid Crystals with CH_2O and CH=N Linkages

报道一类新的、结构通式为MeO2CC6H4CH2OC6H4CH=NC6H4Y,Y=OCnH2n+1,Me,Cl,Br,NO2,H的棒状液晶化合物的合成.通过DSC和偏光显微镜对其介晶性研究发现,除Y=H外,这些化合物均具有介晶性.当Y为非烷氧基时,呈向列相液晶;当Y为较短的烷氧基时(n=1～3),液晶化合物具有向列相(N);Y为较长烷氧基时(n=4～16),液晶化合物只有近晶B相(SB)和近晶A相(SA);SA-I相变的熵变随烷氧链原子数而奇-偶变化,但与N-I相变的“奇-偶效应”相反.

A homolog of new liquid crystals with the structure of MeO2CC6H4CH2OC6H4CH=NC6H4Y, Y =OCnH2n+1 (n=1 similar to 12, 14, 16), Me, Cl, Br, NO2 and H were synthesized and their mesomorphic properties were studied through differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). The result shows that molecules with non-alkyloxy substituent are nematogenic and short alkyloxy chains (n= 1 similar to 3) in the homologue lead to nematic phase with odd-even effect, the molecules with longer alkyloxy chains (n=4 similar to 16) present smectic A and B phases, while the entropy changes of SA to isotropic liquid have opposite 'odd-even effect' to those of the nematic to isotropic transition.